Introduction
Mastitis is a common condition in lactating women; estimates from prospective studies range from 3% to 20%, depending on the definition and length of postpartum follow-up. The majority of cases occur in the first 6 weeks, but mastitis can occur at any time during lactation. There have been few research trials in this area.
Quality of evidence (levels of evidence I, II-1, II-2, II-3, and III) for each recommendation as defined in the U.S. Preventive Services Task Force Appendix A Task Force Ratings is noted in parentheses in this document.
Definition and Diagnosis
The usual clinical definition of mastitis is a tender, hot, swollen, wedge-shaped area of breast associated with temperature of 38.5° C (101.3° F) or greater, chills, flu-like aching, and systemic illness. However, mastitis literally means, and is defined herein, as an inflammation of the breast; this inflammation may or may not involve a bacterial infection. Redness, pain, and heat may all be present when an area of the breast is engorged or “blocked”/“plugged,” but an infection is not necessarily present. There appears to be a continuum from engorgement to noninfective mastitis to infective mastitis to breast abscess. (II-2)
Predisposing Factors
The following factors may predispose a lactating woman to the development of mastitis. Other than the fact that these are factors that result in milk stasis, the evidence for these associations is generally inconclusive (II-2):
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Damaged nipple, especially if colonized with Staphylococcus aureus
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Infrequent feedings or scheduled frequency or duration of feedings
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Missed feedings
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Poor attachment or weak or uncoordinated suckling leading to inefficient removal of milk
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Illness in mother or baby
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Oversupply of milk
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Rapid weaning
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Pressure on the breast (e.g., tight bra, car seatbelt)
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White spot on the nipple or a blocked nipple pore or duct: milk blister or “bleb” (a localized inflammatory response)
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Maternal stress and fatigue
Investigations
Laboratory investigations and other diagnostic procedures are not routinely needed or performed for mastitis. The World Health Organization publication on mastitis suggests that breastmilk culture and sensitivity testing “should be undertaken if
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there is no response to antibiotics within 2 days
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the mastitis recurs
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it is hospital-acquired mastitis
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the patient is allergic to usual therapeutic antibiotics or
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in severe or unusual cases.” (II-2)
Breastmilk culture may be obtained by collecting a hand-expressed midstream clean-catch sample into a sterile urine container (i.e., a small quantity of the initially expressed milk is discarded to avoid contamination of the sample with skin flora, and subsequent milk is expressed into the sterile container, taking care not to touch the inside of the container). Cleansing the nipple prior to collection may further reduce skin contamination and minimize false-positive culture results. Greater symptomatology has been associated with higher bacterial counts and/or pathogenic bacteria. (III)
Management
Effective Milk Removal
Because milk stasis is often the initiating factor in mastitis, the most important management step is frequent and effective milk removal:
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Mothers should be encouraged to breastfeed more frequently, starting on the affected breast.
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If pain interferes with the letdown, feeding may begin on the unaffected breast, switching to the affected breast as soon as letdown is achieved.
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Positioning the infant at the breast with the chin or nose pointing to the blockage will help drain the affected area.
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Massaging the breast during the feed with an edible oil or nontoxic lubricant on the fingers may also be helpful to facilitate milk removal. Massage, by the mother or a helper, should be directed from the blocked area moving toward the nipple.
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After the feeding, expressing milk by hand or pump may augment milk drainage and hasten resolution of the problem. (III)
An alternate approach for a swollen breast is fluid mobilization, which aims to promote fluid drainage toward the axillary lymph nodes. The mother reclines, and with gentle hand motions starts stroking the skin surface from the areola to the axilla. (III)
There is no evidence of risk to the healthy term infant of continuing breastfeeding from a mother with mastitis. Women who are unable to continue breastfeeding should express the milk from breast by hand or pump, as sudden cessation of breastfeeding leads to a greater risk of abscess development than continuing to feed. (III)
Supportive Measures
Rest, adequate fluids, and nutrition are important measures. Practical help at home may be necessary for the mother to obtain adequate rest. Application of heat—for example, a shower or a hot pack—to the breast just prior to feeding may help with the letdown and milk flow. After a feeding or after milk is expressed from the breasts, cold packs can be applied to the breast in order to reduce pain and edema.
Although most women with mastitis can be managed as outpatients, hospital admission should be considered for women who are ill, require intravenous antibiotics, and/or do not have supportive care at home. Rooming-in of the infant with the mother is mandatory so that breastfeeding can continue. In some hospitals, rooming-in may require hospital admission of the infant.
Pharmacologic Management
Although lactating women are often reluctant to take medications, women with mastitis should be encouraged to take appropriate medications as indicated.
Analgesia
Analgesia may help with the letdown reflex and should be encouraged. An anti-inflammatory agent such as ibuprofen may be more effective in reducing the inflammatory symptoms than a simple analgesic like paracetamol/acetaminophen. Ibuprofen is not detected in breastmilk following doses up to 1.6 g/day and is regarded as compatible with breastfeeding. (III)
Antibiotics
If symptoms of mastitis are mild and have been present for less than 24 hours, conservative management (effective milk removal and supportive measures) may be sufficient. If symptoms are not improving within 12 to 24 hours or if the woman is acutely ill, antibiotics should be started. Worldwide, the most common pathogen in infective mastitis is penicillin-resistant S. aureus . Less commonly, the organism is a Streptococcus or Escherichia coli . The preferred antibiotics are usually penicillinase-resistant penicillins, such as dicloxacillin or flucloxacillin 500 mg by mouth four times per day, or as recommended by local antibiotic sensitivities. (III) First-generation cephalosporins are also generally acceptable as first-line treatment, but may be less preferred because of their broader spectrum of coverage. (III)
Cephalexin is usually safe in women with suspected penicillin allergy, but clindamycin is suggested for cases of severe penicillin hypersensitivity. (III) Dicloxacillin appears to have a lower rate of adverse hepatic events than flucloxacillin. Many authorities recommend a 10- to 14-day course of antibiotics ; however, this recommendation has not been subjected to controlled trials. (III)
S. aureus resistant to penicillinase-resistant penicillins (methicillin-resistant S. aureus [MRSA], also referred to as oxacillin-resistant S. aureus ) has been increasingly isolated in cases of mastitis and breast abscesses. (II-2) Clinicians should be aware of the likelihood of this occurring in their community and should order a breastmilk culture and assay of antibiotic sensitivities when mastitis is not improving 48 hours after starting first-line treatment. Local resistance patterns for MRSA should be considered when choosing an antibiotic for such unresponsive cases while culture results are pending. MRSA may be a community-acquired organism and has been reported to be a frequent pathogen in cases of breast abscess in some communities, particularly in the United States and Taiwan. (I, II-2) At this time, MRSA occurrence is low in other countries, such as the United Kingdom. (I) Most strains of methicillin-resistant staphylococci are susceptible to vancomycin or trimethoprim/sulfamethoxazole but may not be susceptible to rifampin. Of note is that MRSA should be presumed to be resistant to treatment with macrolides and quinolones, regardless of susceptibility testing results. (III)
As with other uses of antibiotics, repeated courses place women at increased risk for breast and vaginal Candida infections.
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